Chapter 27. Common Tasks in Python

At this point in the book, you have been exposed to a fairly complete survey of the more formal aspects of the language (the syntax, the data types, etc.). In this chapter, we'll "step out of the classroom" by looking at a set of basic computing tasks and examining how Python programmers typically solve them, hopefully helping you ground the theoretical knowledge with concrete results.

Python programmers don't like to reinvent wheels when they already have access to nice, round wheels in their garage. Thus, the most important content in this chapter is the description of selected tools that make up the Python standard library—built-in functions, library modules, and their most useful functions and classes. While you most likely won't use all of these in any one program, no useful program avoids all of these. Just as Python provides a list object type because sequence manipulations occur in all programming contexts, the library provides a set of modules that will come in handy over and over again. Before designing and writing any piece of generally useful code, check to see if a similar module already exists. If it's part of the standard Python library, you can be assured that it's been heavily tested; even better, others are committed to fixing any remaining bugs—for free.

The goal of this chapter is to expose you to a lot of different tools, so that you know that they exist, rather than to teach you everything you need to know in order to use them. There are very good sources of complementary knowledge once you've finished this book. If you want to explore more of the standard library, the definitive reference is the Python Library Reference, currently over 600 pages long. It is the ideal companion to this book; it provides the completeness we don't have the room for, and, being available online, is the most up-to-date description of the standard Python toolset. Three other O'Reilly books provide excellent additional information: the Python Pocket Reference, written by Mark Lutz, which covers the most important modules in the standard library, along with the syntax and built-in functions in compact form; Fredrik Lundh's Python Standard Library, which takes on the formidable task of both providing additional documentation for each module in the standard library as well as providing an example program showing how to use each module; and finally, Alex Martelli's Python in a Nutshell provides a thorough yeteminently readable and concise description of the language and standard library. As we'll see in Section 27.1, Python comes with tools that make self-learning easy as well.

Just as we can't cover every standard module, the set of tasks covered in this chapter is necessarily limited. If you want more, check out the Python Cookbook (O'Reilly), edited by David Ascher and Alex Martelli. This Cookbook covers many of the same problem domains we touch on here but in much greater depth and with much more discussion. That book, leveraging the collective knowledge of the Python community, provides a much broader and richer survey of Pythonic approaches to common tasks.

This chapter limits itself to tools available as part of standard Python distributions. The next two chapters expand the scope to third party modules and libraries, since many such modules can be just as valuable to the Python programmer.

This chapter starts by covering common tasks which apply to fundamental programming concepts—types, data structures, strings, moving on to conceptually higher-level topics like files and directories, Internet-related operations and process launching before finishing with some nonprogramming tasks such as testing, debugging, and profiling.